1. Field of the Invention
The present invention relates to a carrier for manufacturing a memory device, a method using the same, and a portable memory device using the manufacturing method.
2. Description of Related Art
In recent years, the technology and material of an electronic integrated circuit have been developed rapidly, and the volume of a chip is increasingly reduced, but the function becomes increasingly powerful and the applications thereof have been gradually reached anywhere. Therefore, the products manufactured by using the electronic integrated circuit gradually becomes light, thin, short, and small, such as electronic dictionaries, digital cameras, and various other digital products. Furthermore, because of the gradually mature chip packaging technology, in the current market, a single chip or multiple chips are packaged into a quite slim card, to form a removable memory with a volume smaller than that of an existed magnetic recording medium by utilizing the characteristic that the chip may store a large amount of data. Such electronic media are all called memory card.
Currently, SD (secure digital) memory card is one of the most commonly used memory cards. The SD memory card uses a standard of a flash memory, for example, and is applied in portable devices, such as digital cameras, personal digital assistants (PDA), and multi-media players. The technology of the SD memory card is formed based on a format of a multi-media card (i.e., so-called MMC), but the SD memory card is slightly thicker than the MMC. The SD memory card has a high data transmission rate and the standard with which the SD memory card uses is updated continually. The profile of the common SD memory card is about 32 mm×24 mm×2.1 mm.
In recent years, as the demand for data storage capacity is increased, and the development trends of electronic devices towards light weight, thinness, shortness, and smallness, the substrate area of the memory card is gradually reduced. A miniSD specification was also introduced for the SD cards in the year of 2003, so as to reduce the size of the memory card, for example, the size is about 20 mm×21.5 mm×1.4 mm.
However, as the size of the memory card is increasingly reduced, the size of the memory dies in the memory card is also reduced accordingly, and the used printed circuit board also becomes much thinner and smaller. Under this circumstance, a carrier used in the manufacturing process plays a crucial role. How to ensure the efficiency of the memory card and to protect the components in the memory card from being damaged becomes a topic deserving further consideration.
For example, the memory card meeting the miniSD specification requirement is only 1.4 mm in thick, so the thickness of the employed printed circuit board (PCB) must be lower than 0.16 mm. If such a specification is adopted, during the process of manufacturing the memory cards, PCB manufacturers cannot overcome the problem of the bending of the PCB, i.e., the bowing problem in the field, which also causes the problem that the components cannot be installed successfully by using the Surface Mounted Technology (SMT), or deformation occurs during the reflow process. Accordingly, the problem of empty soldering occurs during a soldering process, and as a result, the flash memory may suffer a short circuit problem. This is also one of the reasons why the yield rate of the manufacturers of the miniSD memory card cannot break through 60%.
Some PCB manufacturers have suggested amending the layout of the PCB to connect the plate edges, i.e., through the manner of the edge connector of gold fingers, which however cannot overcome the aforementioned problems, so the yield rate cannot be enhanced efficiently.
In addition, some SMT manufacturers also employ a two-piece manufacturing carrier, including a bottom plate and a top cover, in which the top cover is used to press each flash memory, so as to overcome the bowing problem of the PCB. However, the conventional method is merely to add the top cover in the reflow process, which can only avoid thermal deformation occurring in the reflow process, but cannot overcome the bowing problem that has already occurred before the material of the PCB is purchased. Therefore, the two-piece manufacturing carrier only may enhance the yield rate by 10%-15%, but the additional operation steps wastes some extra working hours.